The invention relates generally to electronic implants, and more particularly to externally programmable multimode biological tissue stimulators.
Neural stimulators hold great promise for relief from the effects of various physiological disorders. For example, electrodes can be implanted at sites in the human brain for control of neurological disorders or along the spine to block intractable pain. While neural stimulators share many of the characteristics of cardiac pacers, the great variety of neural applications frustrates attempts to adapt pacer technology and to define standard parameters. Rate, width and amplitude requirements vary by factors of ten from one neural application to another. Moreover, the optimum parameters for a given patient may drift widely from time to time.
The complexity of the functional requirements suggests the use of a multi-purpose programmable generalized neural stimulator. For chronic conditions, a fully implanted battery-operated stimulator with telemetry is indicated. Because the pulse rate may greatly exceed the one to two pulse per second (pps) cardiac rate, battery drain, however, is a more acute problem. Moreover, the increased complexity of the programming variables increases the chances for error. Despite the complexity of the overall system, the power consumption and number of electronic components must be kept within bounds. The exceptionally high degree of programmable adaptability and relatively high pulse rate for the ideal neural stimulator require a wholly new approach to both the internal electronics and the external programming.